1. Technical Field of the Invention
The present invention relates to a sensor and more particularly to a sensor, such as a rotary position sensor, which includes a main housing and a rotatable drive arm assembly that is configured to prevent ice locking of the drive arm assembly relative to the main housing.
2. Description of the Prior Art
Various sensors are used in automotive applications. Sensors utilized in such automotive applications must be able to perform their intended function over a relatively wide temperature range, for example, xe2x88x9220xc2x0 F. to 120xc2x0 F., as well as be tolerant of various climate conditions, such as ice, rain and sleet. Of the various sensors utilized in automotive applications, rotary position sensors are known and used in various applications on an automobile, such as sensing the butterfly position on a throttle body (throttle position sensor); sensing the relative position of the vehicle body relative to the chassis (ride height sensor) and sensing the position of the transmission shift lever (transmission shift position sensor). Such sensors, such as the ride height sensor, are located on the underside of an automobile and are thus subject to harsh environmental conditions and potential failure from such conditions. In particular, such rotary position sensors are normally formed with a stationery housing rigidly and a rotatable drive arm assembly. During relatively harsh environmental conditions, moisture is known to seep into the main housing and freeze creating an ice lock condition preventing a rotatable drive arm from rotating. Such a condition causes incorrect position signals to be generated by the rotary position sensor. Accordingly, automotive systems that are responsive to such data may operate improperly. Moreover, ice lock of the drive arm assembly could result in damage or catastrophic failure of the rotary position sensor requiring replacement. Accordingly, there is a need for a rotary position sensor which minimizes if not eliminates an ice lock condition and provides reliable sensor output in all environmental conditions.
Briefly, the present invention relates to a rotary position sensor which includes a molded housing with a central aperture forming a drive arm cavity, a drive arm assembly and a rotor plate. The drive arm assembly carries a circular magnet and a shunt ring and is rotatably received within the drive arm cavity. The drive arm assembly is formed with an extending stud for connection to an external mechanical lever. The rotor plate is used to close the drive arm cavity and carries a magnetic flux responsive element and one or more flux concentrators and optional flux shunt, if required. The molded housing, drive arm assembly and rotor plate are configured to minimize air space within the drive arm cavity after the sensor is assembled. By minimizing air spaces within the drive arm cavity, the amount of ice build up within the drive arm cavity is minimized. In addition, to further prevent a condition of ice lock of the drive arm assembly relative to the molded housing, all surfaces within the drive arm cavity are formed as smooth surfaces.